Investigation On Flow And Evaporation In Small Aspect Ratio Microchannel

In recent years,with the rapid development of micro-nano manufacturing processes and integration levels,chip manufacturing has developed in the direction of miniaturization and high integration.Effective thermal management technology is necessary to ensure the reliable and efficient operation of electronic equipment.Due to the excellent heat dissipation performance,the microchannel cooling technology has more broad application prospects and can meet the heat dissipation requirements of highly integrated chips.With the assistance of visual experimental platform,the thesis investigated the flow and heat transfer characteristics of silicon-based microchannels with small aspect ratio.The effects of changes in aspect ratio and different working fluids on the flow and evaporation characteristics were compared,in order to provide basic data for the design and optimization of microchannel cooling systems.The main research contents and conclusions of this paper are as follows:1?Summarize the progress and current situation of microfludic cooling technology,and review on flow and heat transfer in microchannel with pointing out the shortcomings of the present research.This paper studies the theory and mechanism of capillary flow in the channel,and comprehensively analyzes the influence of factors included dynamic contact angle,bubbles,electroviscosity,and wall roughness on the flow.2?Through the three-time thermal oxidation process,a series of silicon-based microchannels with aspect ratio less than 1(with an aspect ratio of AR=0.217-1.000)are designed and processed.Based on high-speed cameras and optical microscopes,the visual flow and evaporation experimental platforms are built.3?Visualization experiments of flow characteristics of anhydrous ethanol and other working fluids in silicon-based microchannels with small aspect ratio are carried out.The applicability of the LW model is judged by the flow turning moment and the flow parameters.The experimental value is compared with LW theoretical prediction x value.And the difference caused by the dynamic contact angle as the dominant factor is analyzed.On this basis,the flow characteristics of microchannel with variable parameters is studied.By comparing the flow characteristics in the microchannel with the same aspect ratio,the main reason affecting the flow velocity before and after cross-section is the strength of the viscous force.Besides,the effects of different aspect ratio andworking fluids on the flow of silicon-based microchannels with variable parameters are analyzed.4?Visualization experiments of evaporation characteristics of anhydrous ethanol in silicon-based microchannels with small aspect ratio are carried out.Monitor the measurement points and the overall average temperature on the surface of the microchannel,and connect with the evaporation phenomenon in the microchannel.And explore the influence of heat flux density and heating position on the evaporation characteristics,in order to improve the performance of heat dissipation by reducing the formation stage of the liquid bridge.In addition,the evaporation characteristics of microchannel with variable parameters is studied.The microchannel with smaller aspect ratio after cross section has better cooling performance and is suitable for heat dissipation under high heat flux density.Through the comparative analysis of different heating positions,it is concluded that the heating point is closer to the outlet of the microchannel,it is more beneficial to improve the heat dissipation performance of the microchannel.